Various information, such as tire size, brand name, and design, is marked on the side surface of pneumatic tires. To mark such information on the tire side surface, engravings corresponding to this information are engraved on a surface of an annular side plate, which is a component of a tire mold. Upon manufacture of the side plate, various inspections are carried out, including whether the engravings formed on the surface of the side plate match the preset information, whether the position of the engravings is suitable, and whether the engravings have deteriorated.
Such engravings are small being only a few millimeters in size. Thus, visual inspection of the suitability of the engravings requires a great amount of time and effort.
A method of inspection is known that determines the acceptability of a raised or depressed character string formed on a side surface of a manufactured pneumatic tire (see Japanese Unexamined Patent Application Publication No. 2005-246931A). In the method of inspection of this patent document, an image of the raised or depressed character string formed on the tire side surface is captured and an image pattern of the character string is generated. Thereafter, how much the generated image pattern is a match with a preset model pattern is calculated, and this result determines whether the character string is acceptable or not.
In such a method of inspection, a degree of match is obtained by comparing the three-dimensional data of the raised or depressed character string for inspection against a reference (model pattern) raised or depressed character string three-dimensional data. However, processing the data to obtain a degree of match requires much time, and a high performance data processing machine with high processing speeds is required.